Editor's note: This is the second in a series of regional looks at the most competitive House and Senate races to watch in 2016. The West Region includes Alaska, California, Hawaii, Nevada, Oregon and Washington.Nevada Senate: Democrats have only a pair of vulnerable Senate seats, but retiring Sen. Harry Reid’s is one of them. GOP Rep. Joe Heck looks poised to enter the race at any moment, while Democrats are likely to nominate former state Attorney General Catherine Cortez Masto. The last Senate race in a presidential year was in 2012 when appointed-Sen. Dean Heller defeated Democratic Rep. Shelley Berkley by a single point. Democrats are far more confident in Cortez Masto as a candidate, but she is relatively untested for a statewide office holder. Heck has been in tough races, but never statewide. The Rothenberg & Gonzales Political Report /Roll Call rating of the race is Tossup/Tilts Democratic but it is creeping close to a Pure Tossup.

Nevada’s 4th District: GOP Rep. Cresent Hardy is the most vulnerable incumbent in the House. He won a late-breaking race in 2014, 49 percent to 46 percent, over Democratic Rep. Steven Horsford in a cycle in which Democrats completely collapsed in the state. But President Barack Obama won the 4th by 10 points in 2012 and 15 points in 2008 and Democrats are clamoring for the nomination. State Sen. Ruben Kihuen, former Assemblywoman Lucy Flores and wealthy philanthropist Susie Lee are in the race and may be joined by former state Speaker John Oceguera. The Rothenberg & Gonzales Political Report /Roll Call rates the race as Tossup/Tilts Democratic .

Nevada’s 3rd District: If Heck runs for the Senate, his open House seat will be a top Democratic takeover target. Obama won the district narrowly in 2012, and by a wider 9 points in 2008. Heck’s previous victories scared aspiring Democrats over to the 4th District race, but his absence might prompt some of them to make the switch. State Senate Majority Leader Michael Roberson and Las Vegas City Councilman Bob Beers look likely to run on the Republican side. The Rothenberg & Gonzales Political Report /Roll Call rating is Favored Republican with Heck, but a Pure Tossup without him.

California’s 24th District: Democratic Rep. Lois Capps' retirement creates an open-seat opportunity. Last year, the congresswoman’s re-election race tightened and she won 52 percent to 48 percent. But Democrats believe presidential-year turnout will be significantly better. All candidates will run together in the June primary and the top two will move on to the general election. For Republicans, Assemblyman Katcho Achadjian and young businessman Justin Fareed (who finished third in the 2014 primary) will likely battle for one position while Santa Barbara County Supervisor Salud Carbajal and Santa Barbara Mayor Helene Schneider will likely battle for the other. Republicans came close in the midterm last year but a presidential election year should pose a different challenge. The Rothenberg & Gonzales Political Report /Roll Call rates the race as Safe Democrat .

California Senate: The race to replace retiring Democratic Sen. Barbara Boxer is worth watching, even though the seat is not at risk of a Republican takeover. With the Golden State’s top two primary on June 3, there is a chance that state Attorney General Kamala Harris and Rep. Loretta Sanchez, both Democrats, both move on to the general election next November. Either way, Democrats are likely to add at least one minority woman to their Senate caucus in the next Congress. The Rothenberg & Gonzales Political Report /Roll Call rates the race as Safe Democrat. What races would you add to the list?